/* 清除默认间距 */
*{
    margin: 0;
    padding: 0;
}
ul{
    display: flex;
    position: fixed;
    list-style: none;
    height: 50px;
    line-height: 50px;
    left: 0;
    bottom: 0;
    width: 100%;
    background-color: #fff;
}

ul li{
    flex: 1;
    text-align: center;
}

.active{
    color:red;
}